This invention relates to a lower surface contact type contact which is brought into contact, under pressure, with a lower surface of an external contact of a given electronic part as represented by a wiring board, an IC package, etc.
A typical lower surface contact type contact, as schematically shown in FIG. 7, includes an upwardly projecting contact portion 3 which is brought into contact, under pressure, with a lower surface of an external contact 2 of a given electronic part 1. In order to displace the contact portion 3 resiliently downward, the contact portion 3 is supported by a sidewardly expanding curved spring portion 4.
The external contact 2 of the electronic part 1 is placed on the contact portion 3 to press the contact portion 3 downward, so that the curved spring portion 4 is compressed and the contact portion 3 is displaced downward. The restoring force of the curved spring portion 4 causes the contact portion 3 to contact, under pressure, the lower surface of the external contact 2.
The curved spring portion 4 is displaced downward when it is pressed downward by the external contact 2. The curved spring portion 4 naturally includes a downward displacement component F1 and a rightward displacement component F2. Therefore, the curved spring portion 4 is actually moved in a combined direction F3 of the components F1 and F2.
This directly reflects on the movement of the contact portion 3. Specifically, the contact portion 3 moves slantwise downward in the combined direction F3 from a contact start point P1 with respect to the external contact 2 and reaches a contact terminal point P2. As a consequence, a rightward escape (a movement) amount W is inevitably produced between the contact start point P1 of the contact portion 3 and the contact terminal point P2.
This escape amount W causes the contact portion 3 to slide on the lower surface of the external contact 2. In the case where the width of the external contact 2 is small, it gives rise to a problem that the contact portion 3 escapes from the lower surface of the external contact 2. This problem becomes increasingly serious as the external contact is arranged at a smaller pitch. Therefore, a countermeasure is demanded.
The present invention has been accomplished in order to obviate the above problem.